Power transistors commonly employed in automotive and industrial electronics require a low on-state resistance (Ron), while securing a high voltage blocking capability. For example, a MOS (“metal oxide semiconductor”) power transistor should be capable, depending upon application requirements to block drain to source voltages Vds of some tens to some hundreds or thousands of volts. MOS power transistors typically conduct very large currents which may be up to some hundreds of Amperes at typical gate-source voltages of about 2 to 20 V.
Lateral power devices, in which current flow mainly takes place parallel to a main surface of a semiconductor substrate, are useful for semiconductor devices in which further components, such as switches, bridges and control circuits are integrated.
In addition, there are specific requirements regarding the electrical SOA (“safe operating area”). This applies on one side to the linear operation region at higher gate voltages as well as to the resistance to avalanche breakdown at a gate-source voltage of 0 V. In particular, it is desirable to suppress a parasitic bipolar transistor, since the activation of a parasitic bipolar transistor might result in a destruction of the semiconductor device due to the generation of current filaments.